Determinations of the contents of Sr and Ba in a number of specimens of the principal eruptive rock types of the Oslo Region have been made by a semi-quantitative spectrochemical method. The general trends of the resulting figures are in support of the geologically observed age relations within the rock series, all the rocks of monzonitic and similar compositions being comparatively rich in Sr and Ba, and the younger rocks successively poorer. Very striking is the difference between the series biotite nordmarkite - biotite granite on the one hand, and aegirite nordmarkite --ekerite on the other. In the former series Sr and Ba are still moderately abundant, while in the latter they tend to disappear completely.
The absolute concentrations of Sr and Ba in granites, as well as their coefficients of distribution between the felclspar phases of these rocks, seem to be rather insensitive to variations in the temperature of crystallisation.